cdylib-plugin.rs

Introduction

Plugin-style shared libraries are shared libraries that call back into APIs in the host program.

For example, a PostgreSQL extension may use SPI to execute queries in the current transaction.

The host program calls into the plugin, and the plugin calls back into the host program, using symbols defined only in the host program. In the case of a PostgreSQL extension, the number of symbols that a plugin might use is indefinite, because extensions may use any available external or internal API.

Problem

In rust, there are two problems with plugin-style cdylib crates:

1. #62874 On some platforms, linking fails due to the undefined symbols, unless special arguments are passed to the linker.
2. #8193 There is no good way to find the path of the library created.
   1. Makes integration testing difficult.
   2. Makes installation difficult.

Workarounds

Hopefully these problems are solved properly in the future. Until then, cdylib-plugin.rs offers workarounds to these problems.

Add a normal dependency and a build dependency to your crate:

```toml [dependencies]

...

cdylib-plugin = "0.1"

[build-dependencies]

...

cdylib-plugin = "0.1"

```

Add a build.rs in your crate, such as:

```rust extern crate cdylib_plugin;

fn main() { // ... cdylib_plugin::buildflags(); } ```

In your integration tests or installation code, find the library path with cdylib_plugin::cdylib_path().